7x - 10 = 704
x = ....
bậc của đa thức 7x^10+5x^8-6x^9-7x^10 là
A.7 B.8 C.9 D.10
\(\frac{7x}{2.5}+\frac{7x}{5.8}+\frac{7x}{8.11}+\frac{7x}{11.14}+\frac{7x}{14.17}+\frac{7x}{17.20}=\frac{21}{10}\)
tìm x
\(7\frac{x}{2.5}+7\frac{x}{5.8}+.....+7.\frac{x}{17.20}=\frac{21}{10}\)
\(7\left(\frac{x}{2.5}+\frac{x}{5.8}+...+\frac{x}{17.20}\right)=\frac{21}{10}\)
\(\frac{x}{2.5}+\frac{x}{5.8}+...+\frac{x}{17.20}=\frac{21}{70}\)
\(\frac{x.3}{2.5.3}+\frac{x.3}{5.8.3}+...+\frac{x.3}{17.20.3}=\frac{21}{70}\)
\(x.\frac{1}{3}.\left(\frac{3}{2.5}+\frac{3}{5.8}+...+\frac{3}{17.20}\right)=\frac{21}{70}\)
\(x.\frac{1}{3}.\left(\frac{1}{2}-\frac{1}{20}\right)=\frac{21}{70}\)
\(x.\frac{1}{3}.\frac{9}{20}=\frac{21}{70}\)
=> \(x=2\)
\(x=\frac{7x}{2}\)\(-\frac{7x}{5}+\)\(\frac{7x}{5}\)\(-\frac{7x}{8}\)\(+\frac{7x}{8}\)\(-\frac{7x}{11}\)\(+\frac{7x}{11}\)\(-\frac{7x}{14}\)\(+\frac{7x}{14}\)\(-\frac{7x}{17}+\)\(\frac{7x}{17}\)\(-\frac{7x}{20}\)\(=\frac{21}{10}\)
\(x=\frac{7x}{2}\)\(-\frac{7x}{20}\)\(=\frac{21}{10}\)
\(x=\frac{7x.10}{20}\)\(+\frac{7x}{20}\)\(=\frac{21}{10}\)
\(x=\frac{7x.10+7x}{20}\)\(=\frac{21}{10}\)
\(x=\frac{7x.\left(10+2\right)}{20.2}\)\(=\frac{7x.12}{40}\)\(=\frac{21}{10}\)
\(=>\frac{7x.12:4}{40:4}=\)\(\frac{21}{10}\)
\(=>x=1\)
(7x-9)×√7x-10=2x3-7x2+11x
x (7x - 42 ) + 10 (7x -42 ) =0
x.( 7x - 42 ) + 10. ( 7x - 42 ) = 0
=> ( 7x - 42 ). ( x + 10 ) = 0
=> \(\orbr{\begin{cases}x+10=0\\7x-42=0\end{cases}}\)
=> \(\orbr{\begin{cases}x=-10\\x=6\end{cases}}\)
c)3x^2-7x-10=0
d)2x(x-10)-x+10=0
e)3x^3+7x^2+17x+5=0
f)(2x-1)^2-(x-3)^2=0
g)x^3-5x^2+8x=4
c, \(3x^2-7x+10=0\)
\(\Leftrightarrow3x^2+3x-10x+10=0\)
\(\Leftrightarrow3x\left(x+1\right)-10\left(x+1\right)=0\)
\(\Leftrightarrow\left(x+1\right)\left(3x-10\right)=0\)
\(\Leftrightarrow\left[{}\begin{matrix}x=-1\\x=\dfrac{10}{3}\end{matrix}\right.\)
d, \(2x\left(x-10\right)-x+10=0\)
\(\Leftrightarrow2x\left(x-10\right)-\left(x-10\right)=0\)
\(\Leftrightarrow\left(x-10\right)\left(2x-1\right)=0\)
\(\Leftrightarrow\left[{}\begin{matrix}x=10\\x=\dfrac{1}{2}\end{matrix}\right.\)
\(\frac{7x}{2.5}+\frac{7x}{5.8}+\frac{7x}{8.11}+\frac{7x}{11.14}+\frac{7x}{14.17}+\frac{7x}{17.20}=\frac{21}{10}\)tìm x zùm nha nếu không được thì chắc là đề sai đó
Tìm x: | 7x-10 | +7x =10
Giúp mik với , mik đang cần gấp . Ai nhanh tay mik tick cho . Tks
| 7x - 10 | + 7x = 10
| 7x - 10 | = 10 - 7x
=> 7x - 10 thuộc { 10 - 7x; -10 + 7x }
+) 7x - 10 = 10 - 7x
7x + 7x = 10 + 10
14x = 20
x = 10/7
+) 7x - 10 = -10 + 7x
7x - 7x = -10 + 10
0x = 0
=> x = 0
Học tốt O.o
TH1 : x < 10/7
=> / 7x - 10 / +7x = 10 - 7x + 7x = 10 ( luôn đúng )
=> với mọi x < 10/7, ta luôn có / 7x - 10 / + 7x = 10
TH2 : x = 10/7
=> /7x - 10/ + 7x = 0 + 7x = 10
=> x = 10/ 7 ( thỏa mãn )
TH3 : x > 10/7
=> / 7x - 10 / + 7x = 7x - 10 + 7x = 10
=> 14 x = 10
=> x = 10/ 7 ( loại )
Vậy với mọi x < 10/7, biểu thức trên luôn đúng
Ta có :TH1: | 7x-10 | +7x =10
| 7x-10 | = 10-7x
7x-10 = 10-7x
7x+7x = 10-10
14x = 0
=> x=0
TH2: | 7x-10 | = -10-7x
7x-10 = -10-7x
7x+7x = -10+10
14x = 0
=>x=0
giải pt:
a) (x2-3x)(x2+7x+10)=216
b) (2x2-7x+3)(2x2+x-3)+9=0
a) \(\left(x^2-3x\right)\left(x^2+7x+10\right)=216\Rightarrow x\left(x-3\right)\left(x+2\right)\left(x+5\right)=216\)
\(\Rightarrow x\left(x+2\right)\left(x-3\right)\left(x+5\right)=216\Rightarrow\left(x^2+2x\right)\left(x^2+2x-15\right)=216\)
Đặt \(t=x^2+2x\Rightarrow\) pt trở thành \(t\left(t-15\right)=216\Rightarrow t^2-15t-216=0\)
\(\Rightarrow\left(t+9\right)\left(t-24\right)=0\Rightarrow\left[{}\begin{matrix}t=-9\\t=24\end{matrix}\right.\Rightarrow\left[{}\begin{matrix}x^2+2x=-9\\x^2+2x=24\end{matrix}\right.\)
\(TH_1:x^2+2x=-9\Rightarrow x^2+2x+9=0\Rightarrow\left(x+1\right)^2+8=0\) (vô lý)
\(TH_2:x^2+2x=24\Rightarrow x^2+2x-24=0\Rightarrow\left(x-4\right)\left(x+6\right)=0\)
\(\Rightarrow\left[{}\begin{matrix}x=4\\x=-6\end{matrix}\right.\)
b) \(\left(2x^2-7x+3\right)\left(2x^2+x-3\right)+9=0\)
\(\Rightarrow\left(x-3\right)\left(2x-1\right)\left(x-1\right)\left(2x+3\right)+9=0\)
\(\Rightarrow\left(x-3\right)\left(2x+3\right)\left(x-1\right)\left(2x-1\right)+9=0\)
\(\Rightarrow\left(2x^2-3x-9\right)\left(2x^2-3x+1\right)+9=0\)
Đặt \(t=2x^2-3x-9\Rightarrow\) pt trở thành \(t\left(t+10\right)+9=0\)
\(\Rightarrow t^2+10t+9=0\Rightarrow\left(t+1\right)\left(t+9\right)=0\Rightarrow\left[{}\begin{matrix}t=-1\\t=-9\end{matrix}\right.\)
\(TH_1:t=-1\Rightarrow2x^2-3x-9=-1\Rightarrow2x^2-3x-8=0\)
\(\Delta=\left(-3\right)^2-4\left(-8\right).2=73\Rightarrow\left[{}\begin{matrix}x=\dfrac{-b-\sqrt{\Delta}}{2a}=\dfrac{3-\sqrt{73}}{4}\\x=\dfrac{-b+\sqrt{\Delta}}{2a}=\dfrac{3+\sqrt{73}}{4}\end{matrix}\right.\)
\(TH_2:t=-9\Rightarrow2x^2-3x-9=-9\Rightarrow2x^2-3x=0\Rightarrow x\left(2x-3\right)=0\)
\(\Rightarrow\left[{}\begin{matrix}x=0\\x=\dfrac{3}{2}\end{matrix}\right.\)
Tính A=x+y+z biết 19/x+y + 19/y+z + 19/z+x= 7x/y+z + 7x/z+x + 7x/x+y= 133/10
cho (2x+3y)/ (3y+5x)=(5x+7z)/(7z+2x)
tính: (7x+3y+7z)(7x^2+3y^2+7x^2).x^18.y^10.z^1980